1. Field of the Invention
This invention relates to electrical switches such as circuit breakers and overload relays having trip profiles, and more particularly, to apparatus and a method for setting and reading the trip profiles using a portable unit.
2. Background Information
Electrical switches of the types such as circuit breakers and overload relays respond to a set of parameters characterizing current flowing through the switch known as trip profiles to automatically open the switch. In state of the art electrical switches, the trip profiles are implemented by a microprocessor which stores the characterizing parameters in a memory. These trip profiles are established by setting values for the characterizing parameters. Typically, this is performed by a set of switches on the electrical switch. In some cases, rather than having a set of switches on each electrical switch, a portable unit is temporarily connected to the circuit breaker and the profile is set by switches on the portable unit. In some installations, such as for instance in a plant power distribution system, each of the electrical switches, is connected to a remote personal computer which can set the trip profiles remotely.
The trip profiles of state of the art circuit breakers have become quite complex, thereby requiring a certain level of skill and attention to setting them correctly. This is particularly important in systems where the trip profiles of the various switches are coordinated. For instance, in an electric power distribution system the trip profiles of circuit breakers lower in the hierarchy of the distribution system are set so that those circuit breakers will respond before circuit breakers higher up in the hierarchy to thereby isolate a fault as much as possible. The coordination of the trip profiles is performed by a skilled engineer, typically remotely from the distribution system. The various parameters establishing the trip profiles are then taken to the field where they are inserted by other less skilled individuals. This manual setting of the trip profiles is susceptible to human errors, and is otherwise time consuming.
There is a need for an approved apparatus and method for setting trip profiles in electrical switches such as circuit breakers and overload relays, and particularly those controlled by microprocessors.
There is a further need for such an improved method and apparatus which improves the integrity of setting the trip profiles in such electrical switches.
There is yet another need for such an apparatus and method which reduces the time in the field required to set the trip profiles.
There is yet another need for such an apparatus and method which reduces the level of skill required to reliably set the trip profiles in the field.
There is still another need for such an apparatus and method which simplifies and assures the integrity of coordinated trip profiles.
There is a further need for having available a reliable record of trip settings for resetting after breaker maintenance or replacement.